The Nobel committee awarded Colombia’s president, Juan Manuel Santos, the Nobel Peace Prize in an attempt to nudge the peace deal he brokered that was rejected by voters just five days ago.CreditCreditMalin Fezehai for The New York Times

The president of Colombia was awarded the Nobel Peace Prize on Friday for pursuing a deal to end 52 years of conflict with a leftist rebel group, the longest-running war in the Americas, just five days after Colombians rejected the agreement in a shocking referendum result.

Mr. Santos said he was told of the Nobel committee’s decision by his son Martín, who woke him before dawn on Friday. The winner dedicated the prize to his fellow Colombians, especially the victims of the long conflict, and called on the opponents of the peace deal to join him in securing an end to hostilities.

“I invite everyone to join our strength, our minds and our hearts in this great national endeavor so that we can win the most important prize of all: peace in Colombia,” he said alongside his wife during his first public appearance since the Nobel announcement.

But Colombians are so deeply polarized over the issue, it was not clear the prize would do much to shift public opinion. If anything, voters seemed to dig into their positions after the announcement.

“They rushed in giving him this prize,” said Marianella Suárez, 36, who works at a shoe warehouse in Bogotá and voted against the peace deal. “This didn’t seem the right moment. He hasn’t achieved peace, and we don’t know if the FARC will accept jail time for their crimes.”

Jairo Rodríguez, a 49-year-old driver who supported the deal, said he hoped the prize would ease the renegotiation and soften the stances of hard-liners like Álvaro Uribe, Mr. Santos’s predecessor as president, who led the campaign against the deal. “We all want peace,” he said.

Colombian voters threw out the peace deal just days after the government invited world leaders to a celebratory signing ceremony, leaving the fate of the agreement — along with Mr. Santos’s legacy — in limbo.

Despite the setback, the Norwegian Nobel Committee recognized Mr. Santos “for his resolute efforts to bring the country’s more than 50-year-long civil war to an end.”

In announcing the award, Kaci Kullmann Five, the chairwoman of the committee, commended Mr. Santos for starting the process, even as she acknowledged that the people of Colombia had rejected the outcome.

She said she hoped that awarding the prize to Mr. Santos would act as a spur for a future agreement. “The committee hopes that the peace prize will give him strength to succeed in this demanding task,” she said. “Further, it is the committee’s hope that in the years to come, the Colombian people will reap the fruits of the reconciliation process.”

While it remains hard to say what effect it will have, Juan Cristóbal, who researches public opinion and political campaigns at Javeriana University in Bogotá, the Colombian capital, said the main outcome would be to lift morale among the deal’s supporters and the government negotiators.

“It gives more legitimacy to continue this process whose results have left the government exhausted,” he said. “It says to the government: ‘Yes, continue your work.’”

News of the award stirred excitement on Friday in Colombia, where Mr. Santos is the second man from his country to win a Nobel Prize, after the novelist Gabriel García Márquez, who won the literature prize in 1982. Even some who had opposed Mr. Santos in the peace deal offered him well wishes, though they quickly spun the news to their own ends.

“I congratulate President Santos for the Nobel,” Mr. Uribe said . “I want him to lead to change these peace accords that are damaging to democracy.”

Others saw the prize as a blow to opponents like Mr. Uribe. “It’s a call to all those who have, through deception, wanted to throw this process to the ground — that they stop this and that they join this national reconciliation,” said Ivan Cépeda, a senator who was involved in the negotiations.

The prize appeared to breathe life into hopes among supporters that a deal could yet be clinched. “This has given us a boost to push us to keep working for peace,” Silvia Berrocal, the leader of a group backing the deal, said on a radio station Friday morning.

The committee members, whose deliberations are conducted in strict secrecy, have a reputation for surprises, and this year was no exception. While Mr. Santos had been mentioned as a possibility, to many the leading candidate was the White Helmets volunteer search-and-rescue group in Syria. On Friday, its proponents expressed their disappointment on Twitter, even as the group itself sent a note of congratulations to Mr. Santos.

A United States-trained economist from a wealthy family in Bogotá, Mr. Santos rose to power as the defense minister under Mr. Uribe. In that capacity, he organized an intense counterinsurgency campaign that diminished the FARC and wiped out many of its commanders.

As president, Mr. Santos staked his legacy on ending the war. The peace accord, announced in August, was the culmination of four years of negotiations in Havana, as the Colombian government and the rebels worked their way through a series of impasses.

It outlined a timetable for the rebels to abandon their arms and set out a pathway for former fighters to re-enter civilian life — and, in some cases, run for office. The war has claimed about 220,000 lives and displaced more than five million people.

The peace talks brought back old scars, from kidnappings, to the rape of women in rebel camps, to decades of drug trafficking as the FARC muscled its way into the cocaine trade. Mr. Santos resisted calls for tough prison sentences for the FARC, saying that would push them away from the table and back to the war.

The first signs of resistance to the accord emerged this spring, when Mr. Uribe mounted rallies against it and portrayed the president as a “traitor” willing to excuse the FARC’s crimes just to get a deal. Apparently, many Colombians agreed, although they were unwilling to admit as much to pollsters, who had predicted the referendum would win by a wide margin. In the end, it failed narrowly, with 50.2 percent voting against it.

In an interview last month, Mr. Santos said he had struck the right balance in the agreement. “We need to achieve the maximum justice possible, but that would allow us peace,” he said. “I think we struck that equilibrium.”

But he acknowledged lingering concerns about the deal. “Making peace is much more difficult than making war because you need to change sentiments of people, people who have suffered, to try to persuade them to forgive,” he said.

This week, Mr. Santos searched for ways to save the pact, meeting with Mr. Uribe and other opponents. Experts say the two sides may either seek quick changes to the agreement — probably including jail time for some rebel leaders — or engage in a protracted renegotiation. Mr. Santos has warned that a cease-fire with the rebels will expire on Oct. 31.

Asked why the committee had not extended the award to other parties to the negotiation, notably the FARC commander in chief, Rodrigo Londoño, known by his nom de guerre, Timoleón Jiménez, Ms. Kullmann Five said the committee never commented on those who did not receive the award.

But she said that there “are strong reasons to put a light on the president himself,” and that “his role as president” and “the keeper of the process” had been instrumental in securing a deal.

Mr. Londoño, who has pledged to pursue a political solution to the conflict despite the referendum setback, congratulated Mr. Santos and thanked other Latin American countries for aiding the talks.

The committee made its selection from 376 candidates, a record. Of the candidates, 228 were individuals and 148 were organizations. Candidates can be nominated by heads of state, top government officials and lawmakers; certain judges and professors; past winners of the prize; and former and current members of the committee, among others.

The prize amount this year is 8 million Swedish kronor, or about $930,000.

A version of this article appears in print on , on Page A8 of the New York edition with the headline: Colombia’s Leader Is Awarded Nobel Peace Prize for Work to End 52-Year War. Order Reprints | Today’s Paper | Subscribe